1. Field of the Invention
The present invention provides a radio protection method essentially usable in the field of mobile telephony. The object of the invention is to prevent mobile telephones from ringing or being used for calls in sensitive public areas, in particular theaters, cinemas, lecture halls.
2. Description of the Related Art
The systems currently available in university and other auditoriums to prevent mobile telephone use are somewhat simplistic. They are essentially jammers or transmitters that send simple instructions to the mobile telephones, for example instructions to disable the ringer. The jammers transmit jamming signals with a non-negligible power at random and on all frequencies in a range. These jamming signals are superposed on signaling or speech signals addressed to mobile telephones situated in the environment of the jammers. The mobile telephones are incapable of interpreting the signals resulting from such superposition: calls are disconnected.
Such systems have the disadvantage that there is no effective way to limit the areas in which neutralizing noise is broadcast. Consequently some regions that are not to be protected, but which are situated in the vicinity of an area protected in this way, are affected by the broadcast noise. In these areas communication with mobile telephones becomes random or even impossible.
Furthermore, the installation of such jammers is illegal.
Instructions sent to mobile telephones to disable the ringer do not prevent call set-up. The simple transmitters must also have universal means of communicating with these terminals, which is difficult to implement. Not all mobile telephones use the infrared technology, for example. It is nevertheless necessary to solve the problem of one person's call bothering many others by neutralizing not only incoming calls, which activate the ringer of a mobile telephone, but also outgoing calls, if a mobile telephone user attempts to communicate with another party.